1. Field of the Invention
The field of the invention is computerized controllers for controlling a machine or process in an industrial or commercial environment, and more particularly methods for constructing application programs for such controllers.
2. Description of the Background Art
Graphical programming aids, as disclosed in Kossiakoff, U.S. Pat. No. 4,315,315, and Kodosky et al., U.S. Pat. No. 4,901,221, use a programming computer to display a data flow diagram as a graphical representation of a computer program, typically for a second computer. This graphical representation of a computer program is then compiled into an actual program file for operation in the second computer.
For machine or process controllers, several types of graphical programming languages are known. One type is the ladder diagram type, which was developed from relay logic diagrams. The uprights of the ladder diagram represent the high and low side of a power supply circuit. The rungs of the ladder complete a circuit path when the logical elements in the rung are analyzed to produce a logic true result for the rung. Another type of programming language is the sequential function chart, in which an industrial process is analyzed as a series of alternating steps and transitions. Another type of programming language is the function block diagram where a block in a program may be assigned various mathematical, logical or other types of functions to relate inputs to outputs. Before designing a program for an individual controller processor, the controller hardware must be selected and arranged. Controller equipment is sold in units and modules which can be selected and arranged ("configured") in many different numbers and types to make up the system or systems controlling the particular industrial operation. An important consideration in this configuration of the hardware is the determination of the input and output points (I/O points) in the controller system. At these I/O points an input device, for example a pushbutton, sends an electrical signal to the controller system, or an output device, for example a solenoid, receives an output signal from the controller system.
Many controller systems are set up and installed by engineers who specialize in that task. There is a desire to aid a greater number of industrial customers, both large businesses and small, in understanding, installing and using controller equipment. To this end it is desired to provide an easy-to-use and intuitive graphical user interface for a desktop computer, for analyzing an industrial process, configuring the hardware and developing programs for execution by the controller hardware.